Sheet stacking device with air cushion

ABSTRACT

An air blowing unit is arranged so as to blow air toward a side edge of a sheet discharged from a discharging port. Alternatively, the air is blew from below the discharged sheet.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a sheet stacking device that canneatly stack sheets that are discharged by a sheet delivery device(including a printer).

[0002] When sheets, thick or thin, are smooth and flat, due to thefriction produced between the sheets a stacker for a sheet deliverydevice can not stack them neatly. And if the stacking is performed as acontinuous process, paper jamming tends to occur and the sheet deliverydevice would be damaged. Thus, to prevent damage, the sheet deliverydevice must be halted.

[0003] To avoid paper jamming, the sheet stacking device can be tilteddownward, so that sheets are gravity stacked. However, in this casefolding at the distal end of the sheets, or stacking failures due to thecurling of the sheets may occur.

[0004] When further improvements are provided, the sheet delivery devicebecomes larger and more complicated, which is not preferable.

[0005] The reference documents concerning sheet material are JapanesePatent Publication Nos. 4-296594A, 4-327982A and 4-327983A, which wereproposed by the present applicant. And the reference document concerningthe sheet delivery device that employs the above described sheets isJapanese Patent Publication No. 8-132654A, which was also proposed bythe present applicant.

SUMMARY OF THE INVENTION

[0006] It is one objective of the present invention to provide a smalland less expensive stacking device that can stack sheets neatly at apredetermined stacking location, regardless of the shape and thethickness of the sheets, and the material of which they are composed.

[0007] In order to achieve the above object, there is provided a sheetstacking device comprising:

[0008] a sheet discharging port from which a sheet is discharged;

[0009] an air blowing unit for blowing air toward the sheet dischargedfrom the sheet discharging port; and

[0010] a stacker on which the blew sheet is stacked.

[0011] The air blowing unit may be arranged so as to blow the air towarda side edge of the discharged sheet.

[0012] Here, the air blowing unit may be arranged at least one ofdownstream and along the sheet discharging direction such that the airis blew toward the center portion of the discharged sheet in thewidthwise direction thereof.

[0013] Preferably, the air blowing unit blows the air intermittently.

[0014] Here, a cycle of the intermittent blowing is determined inaccordance with the length of the sheet having been discharged.

[0015] Preferably, the air blowing unit blows the air every time 5 to 20cm of the sheet has been discharged.

[0016] Alternatively, the air blowing unit may be arranged so as to blowthe air from below the discharged sheet.

[0017] Preferably, the air blowing unit is arranged in the vicinity ofthe sheet discharging port.

[0018] Preferably, the air blowing unit blows the air intermittently.

[0019] The sheet stacking device may further comprises a sensor fordetecting that the sheet has been discharged from the discharging port.Here, the air blowing unit starts to blow the air upon the detection ofthe sensor and continues blowing the air until the sheet is stacked onthe stacker.

[0020] Preferably, the stacker is arranged so as to support one cornerportion of the blew sheet independent from the size of the sheet.

[0021] According to the present invention, there is also provided amethod of stacking sheets discharged from a sheet discharging port,comprising the steps of:

[0022] blowing air toward the discharged sheet; and

[0023] placing the blew sheet at a predetermined position.

[0024] The air may be blew toward a side edge of the discharged sheet.

[0025] Here, the air is blew from at least one of a downstream area anda side area of the sheet discharging direction such that the air is blewtoward the center portion of the discharged sheet in the widthwisedirection thereof.

[0026] Preferably, the air is blew intermittently.

[0027] Here, a cycle of the intermittent blowing is determined inaccordance with the length of the sheet having been discharged.

[0028] Preferably, the air is blew every time 5 to 20 cm of the sheethas been discharged.

[0029] Alternatively, the air may be blew from below the dischargedsheet.

[0030] Preferably, the air is blew from the vicinity of the dischargingport.

[0031] Preferably, the air is blew intermittently.

[0032] The sheet stacking method may further comprises the steps ofdetecting that the sheet has been discharged from the discharging port.The air blowing is started upon the detection of the sensor andcontinued until the placing step is conducted.

[0033] Preferably, one corner portion of the blew sheet is supportedindependent from the size of the sheet.

[0034] According to the above configuration, air enters a gap betweenindividual stacked sheets, and the contact area between the sheets isreduced. As a result, the sheets can be stacked neatly at apredetermined position, regardless of the shape and the thickness of thesheets, and the material of which they are composed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In the accompanying drawings:

[0036]FIGS. 1A to 1C are schematic diagrams illustrating a sheetstacking device according to a first embodiment of the presentinvention;

[0037]FIGS. 2A to 2C are plan views for explaining an experiment forfinding an appropriate location of an air ejection port; and

[0038]FIGS. 3A to 3C are schematic diagrams illustrating a sheetstacking device according to a second embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039]FIGS. 1A to 1C are schematic diagrams illustrating a sheetstacking device according to the first embodiment of the presentinvention. FIG. 1A is a side view of the sheet stacking device, FIG. 1Bis a front view thereof and FIG. 1C is a plan view thereof.

[0040] A sheet delivery unit 1 comprises: discharging rollers 2, for theexternal discharge of a sheet by the sheet delivery unit 1; an airejection port 3, which is the feature of the present invention; astopper 4; and a slide face 6, along which a sheet 9 that is beingdischarged slides. The slide face 6 also serves as the top of a casingbody for a printer that includes the sheet delivery unit 1. In the firstembodiment, the sheet stacking device is constituted by the air ejectionport 3 from ejected air is directed toward the side of sheet, thestopper 4, a fan (not shown) and the slide face 6.

[0041] An explanation will now be given for the processing performed forthe first embodiment for blowing air from the side of the sheet that isdischarged.

[0042] The sheet 9, while sandwiched between the upper and lowerdischarging rollers 2, is externally discharged by the sheet deliveryunit 1, and is transported along the slide face 6 in the directionindicted by a white arrow shown in FIGS. 1B and 1C. At this time, whenair from the air ejection port 3 is blew against the side of the sheet9, the force exerted in the direction indicated by arrows is applied tothe sheet 9, and the lower edge on the right side of the sheet 9 is heldat the stopper 4.

[0043] Thereafter, the same process is performed for succeeding sheets9, until finally, all the sheets 9 are held and stacked at the stopper4. Since air from the air ejection port 3 enters gaps between theindividual sheets and forms air layers, the contact area for the sheetsis reduced, and a preferable stacked state is provided.

[0044] According to this embodiment, the sheets 9 can be neatly stackedat the predetermined stopper 4, the contact area for the sheets isreduced due to the air layer formed in the gaps between the sheets, anda preferable sheet stacked state is provided.

[0045] In addition, since the lower edge on the right side of the sheet9 is held at the stopper 4 by ejected air, this device can be appliedfor any type of sheet 9, regardless of the sheet size.

[0046]FIGS. 2A to 2C are plan views of a sheet stacking device for whichan experiment was conducted to find an appropriate location for the airejection port 3.

[0047] In the sheet stacking device in FIG. 2A, the air ejection port 3is provided in an area A1 that is located along the sheet deliverydirection, or that is downstream in the sheet delivery direction on theside whereat the stopper 4 is not provided, so that the ejected air isdirected toward the center of the sheet 9.

[0048] In the sheet stacking device in FIG. 2B, the air ejection port 3is provided in an area A2 that is located downstream in the sheetdelivery direction on the side whereat the stopper 4 is provided, sothat the ejected air is directed toward the center of the sheet 9.

[0049] In the sheet stacking device in FIG. 2C, the air ejection port 3is provided in an area A3 that is located upstream in the sheet deliverydirection, so that the ejected air is directed toward the center of thesheet 9.

[0050] As a result of the experiments conducted for the sheet stackingdevices for which the air ejection port 3 was provided in the threedifferent areas A1, A2 and A3:

[0051] (1) For the sheet stacking device in FIG. 2A for which the airejection port 3 was located in area A1, the stacking state wasconsidered to be satisfactory.

[0052] The ejection of air did not need to be performed continuously;intermittent air ejection was sufficient. Specifically, when for onesheet air was intermittently ejected about five times at a pressure of 5to 10 Kg/cm², the stacking state was satisfactory.

[0053] (2) For the sheet stacking device in FIG. 2B for which the airejection port 3 was located in area A2, a stacking state was obtainedthat was inferior to the state obtained in (1). However, when inaddition to the stopper 4 a stopper 4′ was located at a positionindicated by the broken lines, a satisfactory stacking state wasobtained.

[0054] (3) For the sheet stacking device in FIG. 2C for which the airejection port 3 was located in area A3, with a large sheet asatisfactory stacking state was not obtained.

[0055] The reason the stacking state was unsatisfactory is that when alarge sheet is employed the air pressure must be increased, and at ahigh pressure the rear edge of a sheet 9 is attracted to the air nozzledue to the associated air, and that, when the air pressure was low, thesheets could not be stacked neatly.

[0056] From the above results, it is preferable that the air be blownfrom the L-shaped area A1 in FIG. 1C toward the center of the sheet.

[0057] Further, it was found that the air ejection port 3 may be locatedanywhere in area A1 so long as the air is ejected toward the center ofthe sheet 9.

[0058] It was found that the air need not be blown continuously, butintermittently, five times per sheet, to obtain a satisfactory stackingstate. The air pressure at that time was 5 to 10 Kg/cm².

[0059] The intermittent cycle should correlate with the distance thesheet is transported. When the intermittent cycle provides, for example,for air to be ejected once every 5 to 20 cm as the sheet is transported,the same effect as that provided by a continuous operation is obtainedwith a corresponding saving in energy.

[0060] Furthermore, air ejection is required only during a periodextending from the time the sheet 9 is output at the sheet dischargeport until it is halted. Therefore, a sheet sensor (not shown) fordetecting the discharge of the sheet is provided at a proper location,and since the sheet sensor detects a period extending from the time thesheet is discharged until it is halted at the stopper 4, air must beejected continuously or intermittently need only during that period anda saving in energy can be realized.

[0061] As is described above, according to the first embodiment, lessenergy will be consumed and the sheets 9 will be neatly andappropriately stacked at the predetermined stopper 4.

[0062]FIGS. 3A to 3C are schematic diagrams illustrating a sheetstacking device for a second embodiment of the present invention.

[0063]FIG. 3A is a side view of the sheet stacking device, FIG. 3B is afront view thereof, and FIG. 3C is a plan view thereof.

[0064] A sheet delivery unit 1 comprises: discharging rollers 2, for theexternal discharge of a sheet by the sheet delivery unit 1; an airejection port 3, which is the feature of the present invention; astopper 4; a fan 5; and a slide face 6, along which a sheet 9 that isbeing discharged slides. The slide face 6 also serves as the top of acase for the printer that includes the sheet delivery unit 1. The airejection port 3 is located near the sheet discharge port, so that air isejected from the rear of the sheet 9 that is being discharged. In thesecond embodiment the sheet stacking device is constituted by the airejection port 3 through which air is ejected toward the bottom of thesheet, the stopper 4, the fan 5, and the slide face 6.

[0065] An explanation will now be given for the processing for thesecond embodiment for blowing air toward the bottom of a sheet that isdischarged.

[0066] A sheet 9, which is sandwiched between the two upper and lowerdischarging rollers 2, is discharged externally by the sheet deliveryunit 1. When the sheet is discharged by the discharging rollers 2, thefan 5 is rotated and air is blew through the air ejection port towardthe bottom of the sheet 9. The sheet 9 is transported along the slideface 6 in the direction indicated by a white arrow, and is held at thestopper 4.

[0067] Thereafter, succeeding sheets 9 are held at the stopper 4 in thesame manner. Since the force of the air expelled from the air ejectionport 3 is exerted against all the sheets 9 that are held at the stopper4 and an air layer is formed between the individual sheets, the contactarea of the sheets can be reduced and a satisfactory stacking state canbe obtained.

[0068] As the result of various experiments, it was found that for thesecond embodiment the air flow rate is particularly important.

[0069] (1) If the air flow rate was too high, the sheets were raised toomuch. And when rolled sheets were employed, the sheets curled up.

[0070] (2) If the air flow rate was too low, the sheets were not raisedsufficiently, so that the stacking of the sheets was not satisfactory.

[0071] In the second embodiment as well as in the first embodiment, airdid not have to be ejected continuously, and to obtain a satisfactorystacking state air was ejected intermittently, five times for eachsheet. An air flow rate of 70 to 120 litters a minute was used .

[0072] When the air is ejected toward the sheet, the lower edge of theright side of the sheet 9 is held at the stopper, so that thisembodiment can be applied for all types of sheets 9, regardless of thepaper size.

[0073] Further, as in the first embodiment, air ejection is requiredonly during a period extending from the time the sheet 9 is dischargeduntil it is halted. Therefore, a sheet sensor (not shown) for detectingthe discharge of the sheet is provided at a proper position, and sincethe sheet sensor can detect a period extending from the time the sheetis discharged until it is halted at the stopper 4, air must becontinuously or intermittently ejected only during that period, so thata saving in energy can be achieved.

[0074] As is described above, according to the first embodiment, thesheets 9 can be neatly and appropriately stacked at the predeterminedstopper 4, and the consumption of energy can be reduced.

[0075] As is described above, according to the present invention, since(1) air is ejected toward the side of a sheet when it is discharged, or(2) air is ejected toward the bottom of a sheet when it is discharged,sheets can be stacked satisfactorily, regardless of the shape and thethickness of the sheets, and the material of which they are composed.

What is claimed is:
 1. A sheet stacking device comprising: a sheetdischarging port from which a sheet is discharged; an air blowing unitfor blowing air toward the sheet discharged from the sheet dischargingport; and a stacker on which the blew sheet is stacked.
 2. The sheetstacking device as set forth in claim 1, wherein the air blowing unit isarranged so as to blow the air toward a side edge of the dischargedsheet.
 3. The sheet stacking device as set forth in claim 2, wherein theair blowing unit is arranged at least one of downstream and along thesheet discharging direction such that the air is blew toward the centerportion of the discharged sheet in the widthwise direction thereof. 4.The sheet stacking device as set forth in claim 2, wherein the airblowing unit blows the air intermittently.
 5. The sheet stacking deviceas set forth in claim 4, wherein a cycle of the intermittent blowing isdetermined in accordance with the length of the sheet having beendischarged.
 6. The sheet stacking device as set forth in claim 5,wherein the air blowing unit blows the air every time 5 to 20 cm of thesheet has been discharged.
 7. The sheet stacking device as set forth inclaim 1, wherein the air blowing unit is arranged so as to blow the airfrom below the discharged sheet.
 8. The sheet stacking device as setforth in claim 7, wherein the air blowing unit is arranged in thevicinity of the sheet discharging port.
 9. The sheet stacking device asset forth in claim 8, wherein the air blowing unit blows the airintermittently.
 10. The sheet stacking device as set forth in claim 1,further comprising: a sensor for detecting that the sheet has beendischarged from the sheet discharging port, wherein the air blowing unitstarts to blow the air upon the detection of the sensor and continuesblowing the air until the sheet is stacked on the stacker.
 11. The sheetstacking device as set forth in claim 1, wherein the stacker is arrangedso as to support one corner portion of the blew sheet independent fromthe size of the sheet.
 12. A method of stacking sheets discharged from asheet discharging port, comprising the steps of: blowing air toward thedischarged sheet; and supporting the blew sheet at a predeterminedposition.
 13. The sheet stacking method as set forth in claim 12,wherein the air is blew toward a side edge of the discharged sheet. 14.The sheet stacking method as set forth in claim 13, wherein the air isblew from at least one of a downstream area and a side area of the sheetdischarging direction such that the air is blew toward the centerportion of the discharged sheet in the widthwise direction thereof. 15.The sheet stacking method as set forth in claim 13, wherein the air isblew intermittently.
 16. The sheet stacking method as set forth in claim15, wherein a cycle of the intermittent blowing is determined inaccordance with the length of the sheet having been discharged.
 17. Thesheet stacking method as set forth in claim 16, wherein the air is blewevery time 5 to 20 cm of the sheet has been discharged.
 18. The sheetstacking method as set forth in claim 12, wherein the air is blew frombelow the discharged sheet.
 19. The sheet stacking method as set forthin claim 18, wherein the air is blew from the vicinity of thedischarging port.
 20. The sheet stacking method as set forth in claim19, wherein the air is blew intermittently.
 21. The sheet stackingmethod as set forth in claim 12, further comprising the steps of:detecting that the sheet has been discharged from the sheet dischargingport, wherein the air blowing is started upon the detection of thesensor and continued until the supporting step is conducted.
 22. Thesheet stacking method as set forth in claim 12, wherein one cornerportion of the blew sheet is supported independent from the size of thesheet.